Over 80 percent of U.S. women groom their pubic hair, for a wide variety of reasons.

While previous studies have found most women groom their hair "down there" - for example, by shaving, waxing or trimming - until now no one had looked at their motivations, said Dr. Tami Rowen, an obstetrician and gynecologist at the University of California, San Francisco.

It's important to understand what drives women to groom their pubic hair, she and her colleagues say in new report.

Increasingly, women are requesting genital cosmetic surgery, they point out, and in most cases, the women are motivated by aesthetics rather than functionality. Pubic hair grooming might have a role in this trend, "because women are able to visualize their labia more easily now than in the past and are thus more motivated to change their appearance," they say.

In a nationally representative survey of 3,316 women, ages 18 to 65, about 60 percent said they groomed for hygiene and cleanliness. About 46 percent said it was part of their routine and about 32 percent said they thought it made their vagina look nicer.

About 56 percent said they groomed for sex. About 46 percent said they groomed for vacation and 40 percent said they trimmed for a healthcare visit.

"I have noticed over the past couple years that women are extremely self-conscious about their genitals and apologize for not being groomed," Rowen said.

"Women were far more likely to groom if their partner also groomed and if their partner preferred that they groom," the researchers found.

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Frequency of sex, types of sexual activity and sex of sexual partner were not tied to the likelihood of women grooming.

Overall, about 84 percent reported ever grooming their pubic hair, and nearly all said they trimmed it themselves. Removing the hair around or above the vagina was most common followed by trimming the hair on the inner thighs.

White women and those with a college degree were most likely to groom.

Women over age 45 were about 95 percent less likely to groom than younger women, according to the results in JAMA Dermatology.

"There were still a lot of older women who were grooming, but they were grooming far less than the younger women," Rowen told Reuters Health.

The practice may lead to cuts and infections, the researchers note.

Pubic hair serves some important purposes, Rowen said. "It serves as a cushion" between the outside world and the sensitive skin tissues of the vulva, and possibly the labia.

She added, "It traps bacteria, chemicals and various things to prevent them from getting to the vagina and protects the skin from getting irritated."

Rowen said it's still not clear whether trimming of pubic hair makes a difference to vaginal health.

The habit "very much seems to be a cultural trend," she said. "Forty years ago this was not a trend."

She said her team did not do the study to judge people's choice to groom, but she said women should consider their motivations before trimming or permanently removing their hair with lasers.